Various aspects of the present invention relate generally to fuel delivery systems for a kiln such as a cement kiln or lime kiln, and more particularly, to a skewer for the handling of whole tires in the fuel system of a kiln.
Cement is a fine-powdered binding substance that sets when mixed with water to bind sand, gravel and other components into concrete. In general, cement is comprised of two components, including clinker and gypsum. Clinker is produced in a cement kiln by heating raw materials including calcium, silica, alumina, iron and small amounts of various admixtures to a sintering temperature. The resulting clinker exits the kiln in small, irregularly shaped clumps. Gypsum is mixed with the clinker to serve as a setting additive and to facilitate grinding of the clinker into the powdered form of cement.
Several different production processes are known for manufacturing clinker in cement kilns. For instance, cement kilns may be “long dry” or “long wet”. In both cases, the raw materials required to manufacture clinker are crushed and mixed together. In a wet process, the raw material is further mixed with water into a slurry. In each process, the raw material is fed into a long rotary kiln. As the kiln rotates, the raw material is passed from one end of the kiln to the other. The temperature inside the kiln causes the material to undergo chemical changes including calcining and eventually sintering into irregularly shaped clumps. The clumps of clinker are cooled and are ground up in subsequent processes. For instance, the ground up clinker is mixed with gypsum to produce cement, as noted above.
The heating of the kiln contributes to a significant portion of the energy required to operate a cement kiln. As such, the production processing of modern kilns has been modified from conventional long wet and long dry kilns to improve energy efficiency by using a preheater to preheat the raw material before introducing the raw material into the rotary kiln. In early preheater technologies, a riser duct having one or more cyclones feeds the entrance of the rotary portion of the kiln. Essentially, the raw material falling through the preheater to the rotary kiln is heated by the exhaust gas that normally escape from the kiln. An extension of the preheater is the precalciner kiln. In this kiln technology, the preheater efficiency is improved by installing a second heat source in the riser duct.